T Rex not what people think at all.

ew methods of analyzing fossils have scientists arguing more than ever about whether Tyrannosaurus rex was a lumbering scavenger or a swift and agile predator.

A CAT scan study of Tyrannosaurus rex skulls shows it had the inner ear of a much smaller, swifter predator. But a close look inside its thigh bone shows it had the ungainly body of a heavier creature.

"I think what we have to do now is re-model dinosaurs," said Jack Horner of the Museum of the Rockies in Bozeman, Montana.

Lawrence Witmer of Ohio University's College of Osteopathic Medicine and colleagues used computed tomography, a type of X-ray also known as CT or CAT scans, to look at the skulls of more than 100 dinosaur fossils.

"It turns out that inner ear provides some very important clues about behaviors (and) also about their relative movements -- how agile they were or how stately they were," Witmer told a news conference at a meeting of the American Association for the Advancement of Science in St. Louis.

"The hearing part is long and delicate in T. rex, suggesting that it could potentially discriminate sounds effectively and that hearing was important behaviorally."

In comparison, Diplodocus, a large, four-legged herbivore, had a smaller ear canal. "Dinosaurs are famous for their small brains and Diplodocus is a great example of that," Witmer said. "It has an ear that reflects that. It is a very stubby or dumpy-looking ear."

The inner ear also gives clues as to posture and shows that T. rex held its head in an alert, forward-looking position, while Diplodocus looked down, presumably to graze.

And T. rex seems to have an enlarged brain region that is associated with a sense of smell in modern animals, Witmer said.

"This is interesting because T. rex was a gigantic animal. T. rex actually had some very heightened senses," Witmer said. "It also strongly employed relatively rapid turning movements of its eyes and head."

From here.